perf: replace dyn trait objects with concrete types to eliminate vtable overhead

Remove async-trait dependency and use native Rust async fn in traits.
Replace Arc<dyn Trait> with Arc<ConcreteType> throughout the codebase
to enable monomorphization and eliminate dynamic dispatch overhead.

Key changes:
- Remove write-behind cache (no implementation existed)
- Fix should_transcode static method call
- Use ContactStorageAdapter directly instead of dyn AddressBookUseCase
- Clean up unused trait imports across services and DI

https://claude.ai/code/session_01EbAFEfyJNLRmJHmmYDX3Tt

src/interfaces/api/handlers/wopi_handler.rs

@@ -23,6 +23,7 @@ use std::sync::Arc;
 use crate::application::services::wopi_lock_service::WopiLockService;
 use crate::application::services::wopi_token_service::WopiTokenService;
 use crate::infrastructure::services::wopi_discovery_service::WopiDiscoveryService;
+use crate::application::ports::file_ports::{FileRetrievalUseCase, FileUploadUseCase};
 
 /// Shared state for WOPI handlers.
 #[derive(Clone)]